In carbon nanotube fabrication, carbon nanotube bundles may be formed on support catalysts. The carbon nanotube bundles formed on the support catalysts may have a wide range of lengths and diameters. It may be desirable to control the lengths and diameters of the carbon nanotubes. In order to utilize the carbon nanotubes as conductors, it may be useful to metallize the ends of the carbon nanotubes.